This invention relates to the production of fibers from basalt rock. The general technology necessary to produce such fibers is known, and utilizes available equipment and processes. A discussion of basalt, including a review of its chemical composition, microstructure, and physical characteristics, is provided in U.S. Pat. No. 3,557,575, which is hereby incorporated into this disclosure by reference. Similarly, a detailed discussion of the manner by which basalt can be drawn as fibers is provided in U.S. Pat. No. 4,008,094, which also is incorporated by reference. An apparatus for producing fibers of ceramic materials is disclosed in U.S. Pat. No. 3,066,504, which is further incorporated by reference.
The general technology for drawing fibers from basalt is well known and recognized in the literature. A review of this literature is set out in an article titled "Mineral Fiber from Basalt--Potential New U.S. Industry?" by R. A. V. Raff in the periodical Engineering and Mining Journal published in February, 1974. The present disclosure relates to the discovery of an improved process by which the tensile strength of such fibers can be increased beyond those values expected in the use of the prior art processes.